Thallium poisoning is still a source of toxic exposure. Dermatologic changes along with alopecia are key clues to the diagnosis of this painful neuropathy. In this article, the author reviews the clinical and laboratory features.

Key points

• Alopecia is one of the clues to thallium poisoning, as it is almost always present.

• Thallium neuropathy is usually predominately sensory, affecting both small fibers (pain) and large fibers (ataxia).

Historical note and terminology

Pesticides and rodenticides based on thallous salts were commonly used in the past. Although they are rarely used now, poisoning from accidental (mostly children), suicidal, or homicidal ingestion continues to occur (Rusyniak et al 2002; Yumoto et al 2017). Although industrial occupations may result in exposure to thallium, this is usually low level and chronic, rather than acute and high level (Feldman 1999). Consumption of contaminated food and water (Moeschlin 1980; Kuo et al 2005) may also be a source of intoxication. Thallium intoxication has also been reported with contaminated drugs, including heroin and cocaine (Afshari et al 2012).

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